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There's something that distinguishes humans from other animals besides our opposable thumbs: There has never, in the history of the world, been another large vertebrate land animal whose population has grown as much, as quickly or with such devastating consequences as ours. It's safe to assume we're also the only species that will be recognizing World Population Day on Friday, July 11.

World Population Day was designated by the United Nations back in 1989 -- when there were just over 5 billion people in the world -- to highlight the urgency and importance of global population issues. Twenty-five years later, there are more than 7 billion people on the planet -- with 227,000 more added every single day -- and we're not leaving much room for wildlife. Species are going extinct at the fastest rate since the time of the dinosaurs, and studies point to human population growth and overconsumption as the primary drivers.

And it's not just other species feeling the squeeze from our overwhelming growth. We're facing extreme weather driven by climate change, rising sea levels and unprecedented drought. In our daily lives, more of us are noticing never-ending traffic jams and parks turned into parking lots as sprawl takes over some of our last remaining open spaces. The planet is feeling a bit crowded for everyone.

Yet this isn't a topic you're likely to hear around the dinner table. But it needs to be. Not just over dinner, but around the water cooler, at the bar, in the news and on social media. We need to talk about the reality of population growth, what it means for us and the planet, and what we can do about it.

That's why the Center for Biological Diversity, where I work, launched the Crowded Planet campaign in honor of World Population Day. Over the past few weeks, people have been posting photos on Instagram, Facebook and Twitter with the #CrowdedPlanet hashtag showing how living in a world of 7 billion affects their lives and the planet. From wildlife whose home has been turned into golf courses to pristine natural areas that are becoming harder to find, the result has brought new, personal and powerful perspectives to the population conversation.

Want to see more? You can view all of the Crowded Planet photos here or onFacebook. And you can still join the conversation by posting your own photos on social media using the #CrowdedPlanet hashtag. Because talking about these issues is the first step to addressing them.

These images are a snapshot of how population has changed our lives, but with increased access to family planning, reproductive health care and education, we can slow population growth and develop a new picture for the next World Population Day -- one with a positive future for people and wildlife around the world.